This program will be an attempt to identify and characterize the tumour associated and tumour specific antigens of human ladder cancer by two main approaches: 1. Xenogeneic antisera against bladder cancer cell extracts in rabbits, following absorption with normal tissue. 2. Presence of antibodies and cell mediated immune reactions spontaneously occurring in patients with bladder cancer in the autologous and allogeneic situations. The latter studies will be carried out using immunofluorescence, complement dependent cytotoxicity and lymphocyte cytotoxicity predominently. Both surface membrane and cytoplasmic locations of antigens will be studied, including the use of electromacroscopic analysis with immunoperoxidase and the immunohistochemical markers. The same techniques will also be used to identify and localize fetal antigens. These various approaches will enable a comparison to be made between various antigens, and their respective specificities, i.e. unique or common, and lead to the final identification of a pattern of antigens, with subsequent separations immunologically and their significance in the natural history of bladder cancer, both with cancer cells, and in the blood and urine.